Written from the perspective of British policy, this paper notes that a recent Home Office consultation document described individuals with "dangerous and severe personality disorder" (DSPD) as follows: "People who have an identifiable personality disorder to a severe degree, who pose a high risk to other people because of serious antisocial behaviour resulting from their disorder. It does not, by definition, include anybody under the age of 18..." The early origins of DSPD are not addressed despite an evidence base that confirms the life-course persistence of such behaviors. For the purposes of this paper a "developmental disorder" is defined as "a physical or mental condition which starts in childhood, which adversely affects the normal development of the child and which is associated with a range of physical, mental, social, and education impairments during the child's lifetime. Certain developmental disorders may have a life-course-persistent trajectory with continuity into adult life." This paper discusses the links between conduct disorder and antisocial personality disorder, the links between conduct disorder and childhood psychopathy, severe personality disorder and sexual offending, and resilience and protective factors. The paper concludes with the description of a proposed model of severe personality disorder as a developmental disorder. The model encompasses the causal and maintenance processes for the behaviors. The model allows for the emergence of psychiatric disorders, antisocial behaviors, and psychopathic traits that may persist into adult life within a developmental trajectory. The model also has scope for more resilient children to move out of the developmental trajectory and for more vulnerable children to move into this pathway at various stages. 50 references